L or Z 10 year visa? Not sure when I would start the job

I do not speak Chinese, and I want to go to China as a tourist. (A week to a month for starters) However I also have a job offer there, and would like to obtain a 10 year entry permit. I am not sure if I will take the job or not as I want to test it out first. Should I get an L type or Z type? The job offer is to be an oral English teacher, however while English is my first language I will not be going to college for being a teacher or for English. I will be going to college for social work. If I do take the job it would have to be like a paid internship during the winter or summer. Is this possible to do?